Shallow ground improvement, such as less than about 6 feet, is often required when weak or non-uniform subgrade conditions exist. Various techniques and systems have been developed to improve natural ground, pavement foundation, and track bed stiffness values such as chemical stabilization using cement and lime, burying geogrid reinforcement within fill layers, or building up compacted layers of stiffer aggregate. These techniques typically offer treatment depths of less than 1 foot and do not directly build in the desired stiffness while accounting for spatial non-uniformity of stiffness.
By improving stiffness and uniformity, ground can be improved to provide more uniformity support overlying structures and fill, pavement systems can be optimized to reduce pavement layer thickness and long-term pavement performance problems, and railroad track bed can be improved to reduce rail deflections and re-ballasting maintenance. Accordingly, there is continuing need for better and more efficient systems and techniques for improving natural ground, pavement foundation, and track bed stiffness and the associated spatial uniformity of stiffness.